Local Forecast: Bad

By George R. Hendrey and Stephen Pekar

Published: May 6, 2007

THE recent heavy storms that left downtown Manville, N.J., under 10 feet of water; filled the basements of Mamaroneck, N.Y.; and flooded rivers and downed power lines in Connecticut may have provided a glimpse of our future. Climate change is accelerating, and the prognosis for the region is alarming, as it is for the rest of the world. No matter how effectively we begin to curb our greenhouse-gas emissions now, we are destined to see significant climate changes because these gases remain in the atmosphere for a long time. We cannot delay planning for the environmental and human calamities that lie ahead.

All over the world, according to the 2007 scientific report of the United Nations Intergovernmental Panel on Climate Change, ''it is very likely that hot extremes, heat waves and heavy precipitation events will continue to become more frequent.'' But we need look no further than our own backyard to find evidence of warming. Since 1950, average summer temperatures in New York City have increased by seven-tenths of a degree per decade, but for the last 20 years, by more than two degrees per decade.

By the middle of this century, with both temperature and humidity rising, the regional climate will resemble that of today's Maryland, according to the Union of Concerned Scientists. And by 2100, if greenhouse-gas emissions continue to increase at the present rate, New York's heat index could resemble that of northern Georgia, with 60 or more days above 90 degrees and 25 days at over 100 (we now average just two days over 100 a year).

Average sea temperature off our coast has risen by more than two degrees since 1979, and by 2100 it will be four to eight degrees higher. These rising water temperatures will likely lead to stronger and more damaging storms. In 1954, when Hurricane Carol passed over Long Island and hit Connecticut, the tidal surge at New London was 10 feet high. Many scientists feel it is only a matter of time until a truly devastating hurricane makes a direct hit on New York, Connecticut and New Jersey.

Nicholas K. Coch, a hurricane expert at Queens College, predicts that a Category 3 hurricane (the strength of Hurricane Katrina when it hit Louisiana) making landfall just west of the Hudson River Estuary would result in a greatly amplified storm surge, owing to the piling up of coastal waters in the almost right angle formed by the New Jersey and Long Island shores. Surge levels would rise to 20 feet at the Statue of Liberty and more than 26 feet in Jamaica Bay. This would cause extensive flooding of the New Jersey shore, Staten Island and Lower Manhattan, the Rockaways and Coney Island, southern Brooklyn, much of Queens, part of Long Island City and Astoria, and Flushing Meadows-Corona Park and continue on to the Westchester shore.

Rising sea levels will only intensify such storm surges. In the past 100 years, while the global sea level has risen by four to eight inches, water levels in New York Harbor have risen by about a foot, and they are expected to rise five more inches by 2030. Without any controls on greenhouse-gas emissions, the sea level could rise as much as three and a half feet by 2080, Columbia University scientists estimate.

These predictions and actual experience are already depressing property values in low-lying areas and making it more difficult for some homeowners in flood-prone areas to get insurance. As climate change progresses, the economic impact will only increase.

Facing up to climate-driven perils will require comprehensive regional planning. We might consider, for example, ceasing government payments for storm damage to buildings in flood zones. This would gradually reduce and ultimately eliminate housing from the shoreline in New York, New Jersey and Connecticut. If we were to replace the housing with restored wetlands and woodland parks at the water's edge, it would help stabilize the coastline. New sea walls in Lower Manhattan might help protect the city from the high waves created by future hurricanes.

We don't presume to know all of the precautions that will be required, nor their priority and timing, and no one else knows either. What is needed is an international institute, centered in New York, where leaders of the world's great cities along with urban planners, environmental scientists, economists and various other experts can put their knowledge together to prepare for future climate change. We must begin to imagine what may happen, and start investing now, to keep the region safe for this century.